This invention relates to an air conditioning system suitable for an aircraft.
Aircraft air conditioning systems include one or more heat exchangers, an air cycle machine, and conditioning circuits to provide conditioned air for an aircraft cabin and other areas of the aircraft. Typically compressed air, such as bleed air from a turbine engine, is provided to a compressor of the air cycle machine through a heat exchanger. The air is routed to another heat exchanger and through the conditioning circuits before being provided to a turbine. Expanded air from the turbine flows through the conditioning circuits and enters another turbine where the air is further expanded. The further expanded air is provided to a mixer for distribution throughout the aircraft through an air conditioning system pack outlet.
The air conditioning system's requirement for air at elevated pressure to the system varies based upon the altitude and operating condition of the aircraft. For example, higher pressure air is required during ground conditions than high altitude conditions to produce acceptable cooling. As a result, in the prior art more air pressure than needed is required by the air conditioning system at high altitude resulting in inefficient use of aircraft power to generate the higher pressure air.
To improve the efficiency of the air conditioning system and the source providing the high pressure air to the system, a variable pressure source is used so that only the level of pressure needed by the aircraft is provided. For example the air pressure to the aircraft air conditioning system is reduced at high altitudes. However, the prior art air conditioning systems are not configured to run efficiently when the source air pressure is reduced.
What is needed is an air conditioning system that runs efficiently during various altitude conditions to minimize the aircraft power needed for operation.